Now that we have the 'doc' package type, we can avoid generating a
.desktop file without having to mark the packages as an expansion for
a particular base game, which means they won't automatically generate
a dependency on the base game (which is problematic for larry6 because
there is more than one possible base game).
Closes: #913911
Signed-off-by: Simon McVittie <smcv@debian.org>

Right now this is not a functional change (the only other type is
expansion) but it will ensure we do the right thing when documentation
becomes a separate type.
Signed-off-by: Simon McVittie <smcv@debian.org>